Hi,

Please refer to the code:

from odoo import models, api

class SaleOrderLine(models.Model):

    _inherit = 'sale.order.line'

    @api.model_create_multi

    def create(self, vals_list):

        """Automatically add contribution line when a battery/electronic product is added"""

        lines = super().create(vals_list)

        for line in lines:

            product = line.product_id

            order = line.order_id

            # Only add contribution for specific categories

            if product.categ_id and product.categ_id.name in ['Batteries', 'Electronics']:

                # Determine contribution product

                if product.categ_id.name == 'Batteries':

                    contribution_product = self.env.ref('bebat_contribution.product_bebat')

                else:

                    contribution_product = self.env.ref('bebat_contribution.product_recupel')

                # Check if contribution line already exists

                existing = order.order_line.filtered(lambda l: l.product_id == contribution_product)

                if not existing:

                    self.env['sale.order.line'].create({

                        'order_id': order.id,

                        'product_id': contribution_product.id,

                        'name': contribution_product.name,

                        'product_uom_qty': 1,

                        'price_unit': contribution_product.lst_price,

                        'tax_id': [(6, 0, contribution_product.taxes_id.ids)],

                    })

        return lines

Hope it helps.